Synthesis,characterization and properties of polyaniline doped with transition metal substituted silicotungstate

Polyaniline hybrid material doped with transition metal mono-substituted silicotungstate β₂-K₆[SiW₁₁M(H₂O)O₃₉]?·?xH₂O (M?=?Mn²⁺, Co²⁺, Cu²⁺, Fe²⁺) were prepared for the first time. Their scanning electron microscopy (SEM), infrared (IR), UV–Vis, and X-ray diffraction (XRD) patterns confirm the existence of Keggin anions and form the space reticular structure. The material exhibits excellent proton conduction, its proton conductivity is 9?×?10^?2?s?cm^?1 at room temperature (20°C).     

Wide control of proton conductivity in porous coordination polymers

The proton conductivities of the porous coordination polymers M(OH)(bdc-R) [H(2)bdc = 1,4-benzenedicarboxylic acid; M = Al, Fe; R = H, NH(2), OH, (COOH)(2)] were investigated under humid conditions. Good correlations among pK(a), proton conductivity, and activation energy were observed. Fe(OH)(bdc-(COOH)(2)), having carboxy group and the lowest pK(a), showed the highest proton conductivity and the lowest activation energy in this system. This is the first example in which proton conductivity has been widely controlled by substitution of ligand functional groups in an isostructural series.     

Coordination-chemistry control of proton conductivity in the iconic metal-organic framework material HKUST-1

HKUST-1, a metal-organic framework (MOF) material containing Cu(II)-paddlewheel-type nodes and 1,3,5-benzenetricarboxylate struts, features accessible Cu(II) sites to which solvent or other desired molecules can be intentionally coordinated. As part of a broader investigation of ionic conductivity in MOFs, we unexpectedly observed substantial proton conductivity with the "as synthesized" version of this material following sorption of methanol. Although HKUST-1 is neutral, coordinated water molecules are rendered sufficiently acidic by Cu(II) to contribute protons to pore-filling methanol molecules and thereby enhance the alternating-current conductivity. At ambient temperature, the chemical identities of the node-coordinated and pore-filling molecules can be independently varied, thus enabling the proton conductivity to be reversibly modulated. The proton conductivity of HKUST-1 was observed to increase by ~75-fold, for example, when node-coordinated acetonitrile molecules were replaced by water molecules. In contrast, the conductivity became almost immeasurably small when methanol was replaced by hexane as the pore-filling solvent.     

Designable Guest-Molecule Encapsulation in Metal–Organic Frameworks for Proton Conductivity

Metal–organic frameworks (MOFs), as a porous frame material, exhibit considerable electrical conductivity. In recent decades, research on the proton conductivity of MOFs has made gratifying progress. In this review, the designable guest molecules encapsulated into MOFs are summarized and generalized into four types in terms of promoting proton conductive performance, and then recent progress in the promotion of proton conductivity by MOFs encapsulating guest molecules is discussed. The existing challenges and prospects for the development of this strategy for promoting MOFs’ proton conductivity are also listed.     

Preparation and characterization of layer‐by‐layer self‐assembly membrane based on sulfonated polyetheretherketone and polyurethane for high‐temperature proton exchange membrane

A concept of preparing high‐temperature proton exchange membranes with layer‐by‐layer (LBL) self‐assembly technique was proposed and the sulfonated polyetheretherketone (SPEEK) and polyurethane (PU) with 200 LBL deposition cycles denoting (SPEEK/PU)₂₀₀ membrane was prepared in this research. Owing to the strong electrostatic interaction between ? group in SPEEK and ? C? N⁺ group in PU, (SPEEK/PU)₂₀₀ membrane with LBL self‐assembly structure showed a favorable structural stability. The phosphoric acid (PA)‐doped (SPEEK/PU)₂₀₀ membrane showed a higher proton conductivity relative to PA doped SPEEK/PU membrane by solution casting method (SPEEK/PU)₂₀₀/40%PA membrane possessed a proton conductivity value of 2.90 × 10^?2 S/cm at 150 °C under anhydrous conditions. The LBL self‐assembly structure provided a possibility to reduce the negative effect from polymer skeleton blocking charge carrier species even immobilizing protons. Moreover, the (SPEEK/PU)₂₀₀ membrane presented the particularly noteworthy mechanical property even with PA doping. The tensile stress values at break were 72.8 and 24.1 MPa, respectively, for (SPEEK/PU)₂₀₀ and (SPEEK/PU)₂₀₀/40%PA membrane at room temperature, which were obviously higher than the reported values of 15.9 and 2.81 MPa for SPEEK/PU and SPEEK/PU/60%PA membrane. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3446–3454     

Proton and methanol transport behavior of SPEEK/TPA/MCM-41 composite membranes for fuel cell application

This paper reports proton and methanol transport behavior of composite membranes prepared for use in the direct methanol fuel cell (DMFC). The composite membranes were prepared by embedding various proportions (10–30 wt.%) of inorganic proton conducting material (tungstophosphoric acid (TPA)/MCM-41) into sulfonated poly(ether ether ketone) (SPEEK) polymer matrix. The results indicate that the proton conductivity of the membranes increases with increasing loading of solid proton conducting material. The highest conductivity value of 2.75 mS/cm was obtained for the SPEEK composite membrane containing 30 wt.% solid proton conducting material (50 wt.% TPA in MCM-41). The methanol permeability and crossover flux were also found to increase with increasing loading of the solid proton conducting material. Lowest permeability value of 5.7 × 10⁻⁹ cm² s⁻¹ was obtained for composite membrane with 10 wt.% of the solid proton conducting material (40 wt.% TPA in MCM-41). However, all the composite membranes showed higher selectivity (ratio between the proton conductivity and the methanol permeability) compared to the pure SPEEK membrane. In addition, the membranes are thermally stable up to 160 °C. Thus, these membranes have potential to be considered for use in direct methanol fuel cell.     

Anion conducting multiblock copolymers with different tethered cations

A multiblock copoly(arylene ether) polymer was used to quantitatively compare the ion conducting channels formed by three different, tethered cation head‐groups. The synthesis allowed for the formation of an exact number of tethers on each repeat unit. Three head‐groups, quaternary trimethylammonium (TMA), quinuclidium (ABCO), and tris(2,4,6‐trimethoxyphenyl)phosphonium (TTMPP) cation head‐groups were compared in terms of size of the conducting channels, ionic conductivity of the mobile hydroxide ion, mechanical properties, quantity of productive and unproductive water, and chemical stability of the membrane in base. The interdomain spacing showed that multiblock copolymers with larger cations formed larger ion conduction channels in the membrane. Larger cations resulted lower ion exchange capacity (IEC) even though the polymer backbone and tether arrangements were identical. TMA was the most stable cation after exposure to 1 M NaOH at 60 °C for 20 days. ABCO had a lower number of bound water molecules and a 22% loss in ion conductivity after treatment in 1 M NaOH at 60 °C for 20 days due to the higher hydroxide ion concentration in the ion conductive blocks. Membranes with TMA head‐groups also had the best mechanical properties. Two membrane preparation methods were compared. The presence of the cation head‐groups assists in phase segregation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1395–1403     

Determination of ionic conductivity and its impact on proton diffusion model for nickel hydroxide

The ionic conductivity is an important but previously ignored aspect for the nickel hydroxide used in alkaline batteries. With a specially designed device, the ionic conductivity is determined for single beads of spherical nickel hydroxide in KOH solutions. The apparent ionic conductivity is found on the order of 10(-3)-10(-2) S cm-1 in 6 M KOH and to change with the conductivity of the solution in which the bead is immersed. The ionic conductivity of the bead can be mainly attributed to the electrolyte absorbed in the bead. On the basis of these findings, the dual structure model for proton diffusion in spherical nickel hydroxide is refined by specifying nanoparticles to be the component showing a large apparent proton diffusion coefficient (on the order of 10(-7) cm2 s-1). This refined model is able to interpret the main features of the diffusion coefficients reported in the literature, including the unusually large scattering (up to 6 orders of magnitude) and inconsistency in the dependence of proton diffusion coefficient on the state of the charge. Besides, this refined model is supported by the influence of bulk KOH concentration on chronoamperometry and transmission electron microscopy observations.     

Sulfonated Poly(ether ether ketone) and Poly(ethylene glycol) Diacrylate Based Semi-Interpenetrating Network Membranes for Fuel Cells

Polymer electrolyte membranes are prepared from novel semi-interpenetrating polymer network material where the sulfonated poly (ether ether ketone) (SPEEK) is the linear polymer and the poly (ethylene glycol) diacrylate (PEGDA) is the cross-linking constituent. The semi-IPN is prepared by in situ polymerization of PEGDA in the presence of sulfonated poly (ether ether ketone). SPEEK is prepared by direct sulfonation of commercial PEEK (Gatone? 1100) by reported procedures. SPEEK with degree of sulfonation 63% (calculated from FT-NMR) is selected as the base membrane and different semi-IPN membranes were prepared by varying the PEGDA and SPEEK ratio. The degree of sulfonation of SPEEK and the formation of semi-IPN were confirmed by spectroscopy studies. The various semi-IPN membranes were characterized for ion-exchange capacity, water uptake, hydrolytic stability, proton conductivity and thermal stability for evaluating the suitability of these membranes for fuel cells. The proton conductivity of the membranes decreased with increasing PEGDA content. The Semi-IPN membranes exhibited conductivities (30°C) from 0.018 S/cm to 0.006 S/cm. These interpenetrating network membranes showed higher hydrolytic stability than the pure SPEEK membrane. This study shows that semi-IPN membranes based on PEGDA and SPEEK can be viable candidates for electrolyte membranes.     

Water, proton, and oxygen transport in high IEC, short side chain PFSA ionomer membranes: consequences of a frustrated network

The effect of ion exchange capacity (IEC) on the water sorption properties of high IEC, short side chain (SSC) PFSA ionomer membranes, and the relationships between water content, proton conductivity, proton mobility, water permeation, oxygen diffusion, and oxygen permeation are investigated. SSC PFSA ionomer membranes possessing 1.3, 1.4, and 1.5 mmol g(-1) IEC are compared to a series of long side chain (LSC) PFSA ionomer membranes ranging in IEC from 0.9 to 1.13 mmol g(-1). At 25 °C, fully-hydrated SSC ionomer membranes are characterized as possessing higher water contents (56-75 vol%), moderate λ values (15-18), high analytical acid concentrations (2-2.8 M), and moderate conductivity (88-115 mS/cm); but lower than anticipated effective proton mobility. Complementary measurements of water permeability, oxygen diffusion, and oxygen permeability also yield lower than expected values given their much higher water contents. Potential benefits afforded by reducing the side chain length of PFSA ionomer membranes, such as increased crystallinity, higher IEC, and high hydrated acid concentration are offset by a less-developed, frustrated hydrophilic percolation network, which provides a motivation for future improvements of transport properties for this class of material.     

Phosphotungstic acid functionalized silica nanocomposites with tunable bicontinuous mesoporous structure and superior proton conductivity and stability for fuel cells

A novel proton exchange membrane using phosphotungstic acid (HPW) as proton carrier and cubic bicontinuous Ia3d mesoporous silica (meso-silica) as framework material is successfully developed as proton exchange membranes for fuel cells. Meso-silica is functionalized by 80wt% HPW using a vacuum impregnation method. The HPW-functionalized meso-silica (HPW-meso-silica) nanocomposites are characterized by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), N(2) adsorption/desorption isotherms, thermogravimetric analysis (TGA), water uptake and four-probe conductivity. The results show that the mesoporous structure of silica hosts can be altered by the hydrothermal temperature. Conductivity measurements indicate that meso-silica host with pore diameter of 5.0 nm has the highest proton conductivity of 0.11 S cm(-1) at 80 °C and 100% relative humidity (RH) with an activation energy of ～14 kJ mol(-1) and better stability as compared to that with large mesopores. The proton conductivity and performance of HPW-meso-silica nanocomposites also increase with the RH, but it is far less sensitive to RH changes as compared to conventional perfluorosulfonic acid (PFSA) polymers such as Nafion. The maximum power density of the cell with HPW-meso-silcia nanocomposite membranes is 221 mW cm(-2) at 80 °C and 100% RH and decreases to 171 mW cm(-2) when RH is reduced to 20%, a 20% decrease in power output. In the case of a cell with Nafion 115 membranes, the decrease in power density is 95% under identical test conditions. The results demonstrate that the HPW-meso-silica nanocomposite has an exceptionally high water retention capability and is a promising proton exchange membrane material for fuel cells operating at reduced humidity and elevated temperatures.     

A novel proton conductor of imidazole-aluminium phosphate hybrids in the solid state

Anhydrous proton transport at temperatures above 100 °C has attracted considerable attention in the development of fuel cells that operate at intermediate temperatures. Liquid-state imidazole (ImH) is known to be a fast anhydrous proton conductor above 100 °C; however, evaporation and severe conductivity drops above and below its melting point (～90 °C), respectively, are major drawbacks to ImH. In this paper, we report a novel solid-state anhydrous ImH-Al(H(2)PO(4))(3) (AlP) hybrid material prepared via a simple synthesis using mechanical milling. This solid-state hybrid exhibits relatively a high ionic conductivity of ～0.1 mS cm(-1) at 100 °C and remarkably a small activation energy of 0.23 eV. In addition, the ImH-AlP hybrid material provides a means of overcoming both temperature-dependent drawbacks to pure ImH: (1) the ImH-AlP hybrid is thermally stable up to 130 °C, and (2) the hybrid material maintains high ionic conductivity below the melting point of ImH.     

Modulatory Functionalization of Gold Nanorods Using Supramolecular Assemblies

Supramolecular‐assembly‐mediated functionalization of gold nanorods (GNRs) has been developed by reversible phase transfer between water and oils, which offers a facile method for fabricating robust GNRs with surface‐charge tunability. In this regard, trimethylammonium (TMA) GNRs were initially prepared from conventional cetyltrimethylammonium bromide (CTAB) GNRs by means of a ligand‐exchange reaction in the presence of an excess amount of TMA ligands. To further expand their functionality and potential applications, electrostatic assemblies of positively charged TMA‐GNRs with negatively charged oleate ions were prepared. These assemblies (OA‐GNRs) can undergo facile phase transfer from water to hexane. Interestingly, the reversible electrostatic assembly between the TMA and OA ions fabricated onto GNRs can be easily disrupted by treatment with HCl, which removes the OA ions from the GNRs to re‐form the TMA‐GNRs, which can be made soluble in aqueous media again. In addition, OA‐GNRs can be further used for the synthesis of negatively charged GNRs such as 11‐mercaptoundecanoic acid (MUA) GNRs, which are hard to prepare directly from CTAB‐GNRs. This versatile method for phase transfer and functionalization on GNRs is expected to broaden the scope of their applications in sensing, biomedical imaging, photothermal therapies, and drug delivery systems.     

流道与肋宽比对气体扩散层性能影响的数值研究

由于装配压力的作用,气体扩散层产生形变,对质子交换膜燃料电池性能产生影响。国内外学者主要研究气体扩散层形变后对燃料电池性能产生的影响,但对不同流道宽度的燃料电池探究尚不明确。本文采用有限元法建立一个单流道质子交换膜燃料电池三维模型,研究了不同装配压力以及三种流道与肋度比(流道与肋宽比分别为3:2、1:1、2:3)下,气体扩散层厚度变化规律以及它们对孔隙率和电导率的影响。结果显示,随着装配压力的增加,肋下气体扩散层厚度变薄,孔隙率减小,电导率增加;在相同装配压力下,流道与肋宽度比值越大,肋下孔隙率越小,电导率越大。     

Tuning the Halogen/Hydrogen Bond Competition: A Spectroscopic and Conceptual DFT Study of Some Model Complexes Involving CHF2I

Insight into the key factors driving the competition of halogen and hydrogen bonds is obtained by studying the affinity of the Lewis bases trimethylamine (TMA), dimethyl ether (DME), and methyl fluoride (MF) towards difluoroiodomethane (CHF₂I). Analysis of the infrared and Raman spectra of solutions in liquid krypton containing mixtures of TMA and CHF₂I and of DME and CHF₂I reveals that for these Lewis bases hydrogen and halogen‐bonded complexes appear simultaneously. In contrast, only a hydrogen‐bonded complex is formed for the mixtures of CHF₂I and MF. The complexation enthalpies for the C?H ??? Y hydrogen‐bonded complexes with TMA, DME, and MF are determined to be ?14.7(2), ?10.5(5) and ?5.1(6) kJ mol^?1, respectively. The values for the C?I ??? Y halogen‐bonded isomers are ?19.0(3) kJ mol^?1 for TMA and ?9.9(8) kJ mol^?1 for DME. Generalization of the observed trends suggests that, at least for the bases studied here, softer Lewis bases such as TMA favor halogen bonding, whereas harder bases such as MF show a substantial preference for hydrogen bonding.     

一个含有连续氢键的晶态Ni(Ⅱ)⁃MOF的合成、结构及质子传导性能

选用柔性多羧酸有机配体与过渡金属离子Ni(Ⅱ)在水热条件下得到Ni?MOF[Ni2(L)(Nphen)2(H2O)4]n(1)(H4L=5,5'?(丁基?1,4?二氧)间苯二甲酸,Nphen=5?硝基?1,10?邻二氮杂菲)。单晶结构分析表明,配合物1中存在连续氢键作用,这将有利于质子的传导。红外、X射线粉末衍射以及热重分析等表征结果表明,配合物具有良好的纯度和稳定性。将配合物1的颗粒与Nafion混合形成复合膜,并对其进行了电化学研究。结果表明配合物1的掺杂能够明显改善Nafion膜的质子传导行为,复合膜的质子电导率比纯Nafion膜提升24.08%。     

Synthesis, characterization and proton transport properties of mixed metal phosphonate-zirconium titanium hydroxy ethylidene diphosphonate

Novel hybrid material, zirconium titanium hydroxy ethylidene diphosphonate (ZTHEDP) of the class of tetravalent bimetallic acid (TBMA) salt was synthesized using sol-gel route. ZTHEDP was characterized for elemental analysis (zirconium, titanium and phosphorus by ICP-AES and carbon and hydrogen by CHN analyzer), spectral analysis (FTIR), thermal analysis (TGA), X-ray diffraction studies and SEM. Chemical resistivity of this material was assessed in various media-acids, bases and organic solvents. The protons present in the structural hydroxyl groups in ZTHEDP indicate good potential to exhibit solid state proton conduction. The proton transport property of ZTHEDP was explored by measuring specific conductance at different temperatures in the range of 303–423 K at 10 K intervals, using Solartron Impedance Analyzer (SI 1260) over a frequency range 1 Hz-32 MHz at a signal level below 1 V. Zirconium hydroxy ethylidene diphosphonate (ZrHEDP) and titanium hydroxy ethylidene diphosphonate (TiHEDP) were also synthesized under identical conditions, characterized and their proton transport properties investigated for comparative studies. It is observed that, in all cases, conductivity decreases with increasing temperature. Conductivity performance of ZTHEDP, ZrHEDP and TiHEDP is discussed based on conductivity data and activation energy. It is observed that, ZTHEDP exhibits enhanced conductance and the mechanism of transportation is proposed to be Grotthuss type.     

Energy material - the role of silicotungstic acid and fly ash in sulfonated poly (ether sulfone) composites for PEMFC applications

The composite polymer electrolyte membranes were prepared from sulfonated poly (ether sulfone) (SPES), silicotungstic acid (STA) and fly ash (FA). Post sulfonation process was adopted to synthesize SPES using sulphuric and chlorosulfonic acid. The prepared electrolyte membranes were examined by water uptake capacity, swelling ratio, ion-exchange ability, proton conductivity, thermal stability and electrochemical performance for evaluating the pertinence of these membranes in fuel cell applications. As such the pristine membrane restricts with the proton conductivity of 0.042?S cm^?1 at 30?°C and 0.060?S cm^?1 at 90?°C while the polymer composite membrane, SP-STA-FA-10 reveals the maximum conductivity of 0.054?S cm^?1 at 30?°C and 0.073?S cm^?1 at 90?°C. It also exhibits good thermal stability than that of the pure membrane. The membrane electrode assemblies (MEAs) have been successfully developed from SPES as well as SP-STA-FA-10 membranes and their electrochemical performance were studied the wide range of current density. Herein, the composite membranes derived from SPES, STA and FA can be viable candidates for fuel cell applications.     

壳聚糖固体聚合物电池用膜

壳聚糖是甲壳素脱乙酰基的产物，具有良好的成膜性、生物相容性、环保以及价格低廉等特点。作为一种碱性高分子膜材料，近年来已成为聚电解质研究领域中的研究热点。本文综述了壳聚糖固体聚合物电池用膜的研究现状，其改性工艺主要包括共混、化学改性、质子酸掺杂、无机盐掺杂等方法，比较了各种工艺处理后壳聚糖固体聚合物电解质膜的性能差异，并就壳聚糖固体聚合物电解质膜中离子传导机理中有待解决的问题进行探讨，并提出了进一步改进壳聚糖固体聚合物电解质膜性能的研究思路。     

Enhanced and Optically Switchable Proton Conductivity in a Melting Coordination Polymer Crystal

The melting behavior of a coordination polymer (CP) crystal was utilized to achieve enhanced and optically switchable proton conductivity in the solid state. The strong acid molecules (triflic acid) were doped in one‐dimensional (1D) CP, [Zn(HPO₄)(H₂PO₄)₂](ImH₂)₂ (ImH₂=monoprotonated imidazole) in the melt state, and overall enhancement in the proton conductivity was obtained. The enhanced proton conductivity is assigned to increased number of mobile protons and defects created by acid doping. Optical control over proton conductivity in the CP is achieved by doping of the photo acid molecule pyranine into the melted CP. The pyranine reversibly generates the mobile acidic protons and local defects in the glassy state of CP resulting in the bulk switchable conductivity mediated by light irradiation. Utilization of CP crystal in liquid state enables to be a novel route to incorporate functional molecules and defects, and it provides a tool to control the bulk properties of the CP material.